This study proposes to establish a cohort of patients with inflammatory arthritis of less than one year's duration in an attempt to better understand pathogenetic mechanisms involved in early synovitis and to determine prognostic factors associated with the clinical disease course. Synovial biopsies and synovial fluid will be obtained to search for microbial agents and other initiating and modulating factors that may be most readily distinguished early in the disease and to determine the stage of disease at which certain immunologic and hormonal changes become evident. Specimens will be evaluated by polymerase chain reaction and immunoelectron microscopy for the presence of infectious agents such as difficult to culture chlamydia and to assess cytokine profiles present with the synovial membrane. The study will search for genetic, in particular HLA DR loci, and other features that may be associated with specific forms of inflammatory arthropathies that might predict the subsequent clinical disease course or response to different agents used in treatment of rheumatoid arthritis and other types of chronic inflammatory arthropathies. Assessments of the neuroendocrine axis suggest that low cortisol or androgens favor development of rheumatoid arthritis. These studies will contribute to knowledge about the early pathogenic events in early arthritis and have the potential to assist in development of new approaches to patient management.